RT8008
1.5MHz, 600mA, High Efficiency PWM Step-Down DC/DC
Converter
General Description
The RT8008 is a high-efficiency pulse-width-modulated
(PWM) step-down DC-DC converter. Capable of delivering
600mA output current over a wide input voltage range from
2.5V to 5.5V, the RT8008 is ideally suited for portable
electronic devices that are powered from 1-cell Li-ion
battery or from other power sources within the range such
as cellular phones, PDAs and handy-terminals.
Internal synchronous rectifier with low R
DS(ON)
dramatically
reduces conduction loss at PWM mode. No external
Schottky diode is required in practical application. The
RT8008 automatically turns off the synchronous rectifier
while the inductor current is low and enters discontinuous
PWM mode. This can increase efficiency at light load
condition.
The RT8008 enters Low-Dropout mode when normal PWM
cannot provide regulated output voltage by continuously
turning on the upper P-MOSFET. RT8008 enter shutdown
mode and consumes less than 0.1µA when EN pin is pulled
low.
The switching ripple is easily smoothed-out by small
package filtering elements due to a fixed operation
frequency of 1.5MHz. This along with small SOT-23-5 and
TSOT-23-5 package provides small PCB area application.
Other features include soft start, lower internal reference
voltage with 2% accuracy, over temperature protection,
and over current protection.
Features
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+2.5V to +5.5V Input Range
Adjustable Output From 0.6V to V
IN
1.0V, 1.2V, 1.5V, 1.8V, 2.5V and 3.3V Fixed/
Adjustable Output Voltage
600mA Output Current, 1A Peak Current
95% Efficiency
No Schottky Diode Required
1.5MHz Fixed-Frequency PWM Operation
Small SOT-23-5 and TSOT-23-5 Package
RoHS Compliant and 100% Lead (Pb)-Free
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Applications
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Cellular Telephones
Personal Information Appliances
Wireless and DSL Modems
MP3 Players
Portable Instruments
Ordering Information
RT8008(-
)
Package Type
B : SOT-23-5
J5 : TSOT-23-5
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Output Voltage
Default : Adjustable
10 : 1.0V
12 : 1.2V
15 : 1.5V
18 : 1.8V
25 : 2.5V
33 : 3.3V
Note :
RichTek Pb-free and Green products are :
Pin Configurations
(TOP VIEW)
EN
GND
LX
1
2
3
4
VIN
5
FB/VOUT
}
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
SOT-23-5/TSOT-23-5
}
Suitable for use in SnPb or Pb-free soldering processes.
}
100% matte tin (Sn) plating.
DS8008-04 March 2007
www.richtek.com
1
RT8008
Typical Application Circuit
4
C
IN
4.7uF
1
EN
3
L
2.2uH
V
OUT
V
IN
2.2V to 5.5V
VIN
RT8008
LX
VOUT
GND
2
5
C
OUT
10uF
Figure 1. Fixed Voltage Regulator
L
2.2uH
V
OUT
C1
R1
5
I
R2
R2
C
OUT
10uF
V
IN
2.2V to 5.5V
4
C
IN
4.7uF
1
VIN
LX
3
RT8008
EN
GND
2
FB
V
OUT
=
V
REF
R1
x
1
+
R2
with R2 = 300kΩ to 60kΩ so the I
R2
= 2µA to 10µA,
and (R1 x C1) should be in the range between 3x10
-6
and 6x10
-6
for component selection.
Figure 2. Adjustable Voltage Regulator
Layout Guide
V
IN
GND
C
IN
C
OUT
V
OUT
V
IN
C
IN
GND
C
OUT
V
OUT
L
VIN
4
3
2
VOUT
5
1
LX
GND
C1
EN
R1
GND
V
OUT
FB
R2
GND
5
1
EN
VIN
4
3
2
LX
GND
L
Figure 3
Layout note:
1. The distance that C
IN
connects to V
IN
is as close as possible (Under 2mm).
2. C
OUT
should be placed near RT8008.
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2
DS8008-04 March 2007
RT8008
Functional Pin Description
Pin Number
1
2
3
4
5
Pin Name
EN
GND
LX
VIN
FB/VOUT
Pin Function
Chip Enable (Active High, do not leave EN pin floating, and V
EN
< V
IN
+ 0.6V).
Ground.
Pin for Switching.
Power Input.
Feedback Input Pin.
Function Block Diagram
EN
VIN
OSC &
Shutdown
Control
Slope
Compensation
Current
Sense
RS1
Current
Limit
Detector
FB/VOUT
Error
Amplifier
RC
COMP
PWM
Comparator
Control
Logic
Driver
LX
UVLO &
Power Good
Detector
Zero
Detector
V
REF
RS2
GND
DS8008-04 March 2007
www.richtek.com
3
RT8008
Absolute Maximum Ratings
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(Note 1)
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Supply Input Voltage ---------------------------------------------------------------------------------------------------- 6.5V
Enable, FB Voltage ------------------------------------------------------------------------------------------------------ V
IN
+ 0.6V
Power Dissipation, P
D
@ T
A
= 25°C
SOT-23-5, TSOT-23-5 --------------------------------------------------------------------------------------------------- 0.4W
Package Thermal Resistance (Note 4)
SOT-23-5, TSOT-23-5,
θ
JA
---------------------------------------------------------------------------------------------- 250°C/W
SOT-23-5, TSOT-23-5,
θ
JC
--------------------------------------------------------------------------------------------- 130°C/W
Junction Temperature Range ------------------------------------------------------------------------------------------ 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------ 260°C
Storage Temperature Range -------------------------------------------------------------------------------------------
−
65°C to 150°C
ESD Susceptibility (Note 2)
HBM (Human Body Mode) --------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------------- 200V
(Note 3)
Recommended Operating Conditions
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Supply Input Voltage ---------------------------------------------------------------------------------------------------- 2.5V to 5.5V
Junction Temperature Range ------------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------------
−
40°C to 85°C
Electrical Characteristics
(V
IN
= 3.6V, V
OUT
= 2.5V, V
REF
= 0.6V, L = 2.2µH, C
IN
= 4.7µF, C
OUT
= 10µF, T
A
= 25°C, I
MAX
= 600mA unless otherwise specified)
Parameter
Input Voltage Range
Quiescent Current
Shutdown Current
Reference Voltage
Adjustable Output Range
Symbol
V
IN
I
Q
I
SHDN
V
REF
V
OUT
∆V
OUT
∆V
OUT
∆V
OUT
Test Conditions
Min
2.5
Typ
--
50
0.1
0.6
--
--
--
--
--
--
--
--
--
Max
5.5
100
1
0.612
V
IN
−
0.2
+3
+3
+3
+3
+3
+3
+3
+3
Units
V
µA
µA
V
V
%
%
%
%
%
%
%
%
I
OUT
= 0mA, V
FB
= V
REF
+ 5%
EN = GND
For adjustable output voltage
--
--
0.588
V
REF
V
IN
= 2.2 to 5.5V, V
OUT
= 1.0V
0A < I
OUT
< 600mA
V
IN
= 2.2 to 5.5V, V
OUT
= 1.2V
0A < I
OUT
< 600mA
V
IN
= 2.2 to 5.5V, V
OUT
= 1.5V
0A < I
OUT
< 600mA
V
IN
= 2.2 to 5.5V, V
OUT
= 1.8V
0A < I
OUT
< 600mA
V
IN
= 2.8 to 5.5V, V
OUT
= 2.5V
0A < I
OUT
< 600mA
V
IN
= 3.5 to 5.5V, V
OUT
= 3.3V
0A < I
OUT
< 600mA
V
IN
= V
OUT
+ 0.2V to 5.5V, V
IN
≧
3.5V
0A < I
OUT
< 600mA
V
IN
= V
OUT
+ 0.4V to 5.5V, V
IN
≧
2.2V
0A < I
OUT
< 600mA
−3
−3
−3
−3
−3
−3
−3
−3
Fix
∆V
OUT
Output Voltage
Accuracy
∆V
OUT
∆V
OUT
Adjustable
∆V
OUT
To be continued
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4
DS8008-04 March 2007
RT8008
Parameter
FB Input Current
PMOSFET R
ON
Symbol
I
FB
V
FB
= V
IN
V
IN
= 3.6V
V
IN
= 2.5V
V
IN
= 3.6V
V
IN
= 2.5V
Test Conditions
Min
−50
--
--
--
--
1
1.5
--
--
--
f
OSC
T
SD
V
IN
= 3.6V, I
OUT
= 100mA
1.2
--
--
100
V
IN
= 3.6V, V
LX
= 0V or V
LX
= 3.6V
−1
Typ
--
0.3
0.4
0.25
0.35
--
--
--
1.8
0.1
1.5
160
50
--
--
Max
50
--
--
--
--
1.8
--
0.4
--
--
1.8
--
--
--
1
Units
nA
Ω
Ω
A
V
V
V
V
MHz
°C
ns
%
µA
P
RDS(ON)
I
OUT
= 200mA
NMOSFET R
ON
P-Channel Current Limit
EN High-Level Input Voltage
EN Low-Level Input Voltage
Undervoltage Lock Out threshold
Hysteresis
Oscillator Frequency
Thermal Shutdown Temperature
Min. On Time
Max. Duty Cycle
LX Leakage Current
N
RDS(ON)
I
OUT
= 200mA
I
P(LM)
V
ENH
V
ENL
V
IN
= 2.5V to 5.5 V
V
IN
= 2.5V to 5.5V
V
IN
= 2.5V to 5.5V
Note 1.
Stresses listed as the above
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2.
Devices are ESD sensitive. Handling precaution recommended.
Note 3.
The device is not guaranteed to function outside its operating conditions.
Note 4.
θ
JA
is measured in the natural convection at T
A
= 25°C on a low effective single layer thermal conductivity test board of
JEDEC 51-3 thermal measurement standard. Pin 2 of SOT-23-5/TSOT-23-5 packages is the case position for
θ
JC
measurement.
DS8008-04 March 2007
www.richtek.com
5
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